Endoluminal prostheses for treatment of arterial disease have come into wide use over the past several years. Typically, such prosthesis include a luminal graft material of woven polyethylene terephthalate (PET) supported by self-expanding stents, which are often formed of a shape memory alloy.
Endoluminal stent grafts, so called because they are deployed within a lumen of a blood vessel, are employed to support diseased arterial tissue, such as arterial tissue that has been weakened to thereby form aneurysms, psuedoaneurysms, dissections, penetrating ulcers, and intramural hematomas. Arteries that are most susceptible to these type of disease states, and which would be treatable by implantation of endoluminal stent grafts include, for example, the abdominal aorta, the thoracoabdominal aorta, the descending thoracic aorta, the aortic arch, and the ascending aorta.
Generally, endoluminal prostheses are implanted by femoral access through the femoral artery of a patient. Alternatively, endoluminal devices can be implanted by transapical access through the apex of the heart and the left ventricle to, for example, the ascending aorta and may, when deployed, essentially abut the aortic valve at the sinotubular junction, the region of the ascending aorta between the aortic sinuses (of Valsalva) and where the normal configuration of the aorta is attained.
Implantation of a self-expanding stent graft prosthesis generally requires that it be constrained within a narrow diameter during delivery to the deployment site within the patient. Often, the diameter is constrained by containing the prosthesis within at least one sheath that is capped at a distal end, respective to the surgeon, with a pliable nose cone. The sheath and nose cone are guided through the lumen of the artery by a guidewire that extends axially through and extends from the nose cone of the delivery device within which the prosthesis is contained. Once the nose cone and sheath have been advanced to the surgical site where the prosthesis is to be deployed, the sheath containing the prosthesis can be rotated, if necessary, to properly orient the prosthesis, and then one or more sheaths are retracted to allow the prosthesis to expand, thereby deploying the prosthesis at the intended treatment site.
Several problems can occur by remote deployment of endoluminal prosthesis from a constraining sheath. For example, if the portion of the aorta where the prosthesis is to be deployed has an extreme tortuosity or tight radius of curvature, such as the arch of the aorta, which is arcuate, or because the disease state of the aorta has caused the aorta to have an irregular shape, simple retraction of the sheath, or sheaths, from the prosthesis can cause the proximal end (cranially, with respect to the patient) of the stent graft to fail to properly align with the arterial wall. For example, a portion of the proximal end of the stent graft can rotate backward, toward the surgeon, adjacent to the curve in the vessel thereby causing a failure of the proximal end of the stent graft to form a seal with the artery. This phenomenon is commonly referred to as a “retroflex.” Most commonly, rotation of a portion of the proximal end of the stent graft during deployment occurs at an inferior side of a stent graft being deployed within the aortic arch, which has a relatively large diameter. Another problem includes the formation of a “bird's beak,” also referred to as a “gap,” caused by the stent graft failing to properly conform to an inferior portion curve of the aorta, which most commonly occurs as a result of a deployment sequence that forces the most proximal covered stent of the prosthesis to be deployed last.
Another problem occurs when the stent graft must be deployed close to the junction between the ascending aorta and the aortic valve. Specifically, the nose cone employed to assist guidance of the endoluminal prosthesis to the surgical site restricts the ability of the surgeon to deploy the prosthesis contained in the sheath as close to the ascending aorta at its point of origin.
Therefore, a need exists for a delivery system for implanting a prosthesis and methods of implanting a prosthesis that minimizes or overcomes the above-referenced problems.